Quantitative Measures of Past Exposures – A New Asbestos Example
Researchers continue to increase the volume of quantitative data available taken from tissue to better understand past exposures in persons with disease. Asbestos lung fiber burden measurements provide one of many examples. In a new paper, a group of researchers in Japan provide data on lung burdens, and find decreasing fiber burdens in persons with mesothelioma. The article is free online in full text. The abstract provides the following overview:
"Objectives: We aimed to elucidate changes in asbestos and non-asbestos fibre concentrations in the lung tissues of Japanese patients with mesothelioma over time.
Methods: Lung tissues were obtained from 46 patients with mesothelioma who died or underwent surgery between 1971 and 2005. All of the patients had a history of occupational asbestos exposure. We classified patients into four groups according to the period during which their lung tissue was obtained. Asbestos and non-asbestos fibre concentrations were determined by transmission electron microscopy with energy-dispersive X-ray analysis using a low-temperature ashing procedure.
Results: From the 1970s to the 2000s, we observed a decrease in the geometric mean of total asbestos concentration (67.4–1.05 million fibres per gram dry lung), chrysotile concentration (25.0–0.66 million fibres per gram dry lung), amphibole asbestos concentration (21.3–0.76 million fibres per gram dry lung), and non-asbestos fibre concentration (326–19.3 million fibres per gram dry lung). The mean duration of asbestos exposure decreased from 33.7 to 17.6 years, and the mean duration since the last exposure increased from 0.3 to 21.5 years. The percentage of longer fibres to total fibres tended to increase over time, whereas the mean fibre length did not differ significantly.
Conclusions: The present study suggested that asbestos and non-asbestos fibre concentrations in the lung tissues of Japanese patients with mesothelioma who have occupational histories of asbestos exposure may have decreased from the 1970s to the 2000s."